In surveillance work it is sometimes necessary to employ a radio transmitter that can be concealed so as not to attract unwanted attention.
Concealment of small radio transmitters in unobvious locations is known in the art. Various difficulties, however, must be overcome in concealment, since the radio transmitter requires for its operation both power supply devices and an antenna and other parts that tend to be bulky.
It is therefore an object of the present invention to provide a radio transmitter that is both concealable in a small enclosure which is unobtrusive, yet provides enough radiated energy to be readable at a distance sufficient to allow inconspicuous monitoring and has adequate stored electrical energy to remain in operation for the length of time required for most surveillance operations, i.e. at least several hours.
Applicant has found that a conventional tape measure housing with suitable modifications can provide an enclosure for a concealed radio transmitter adapted to fit into the tape measure housing.